Vinylidene chloride polymer compositions having improved low temperature properties



United States Patent "O EBENE CHLRIDE PLYMER COMPSI- TIONS HAVKNG lll/@ROVER LW TEMPERA- TURE PROPERTEES George J. Butzler, Carl P. Zupic, and George B. Sterling,

Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed .lune 13, 1962, Ser. No. 202,062 14 Claims. (Cl. 26S-31.3)

This invention relates to polymeric compositions and, in particular, to polymeric compositions based on vinylidene chloride polymers and copolymers.

Polymers and copolymers of vinylidene chloride with such comonomers as acrylonitrile, vinyl chloride, and lower alkyl acrylates have found wide use as films or packaging of foodstuffs and `other articles. Such films possess many useful properties, such as inertness, ability to be heat sealed, transparency, shrinkability, and low water vapor transmission rates, which are desirable for packaging foodstuffs. However, the prior vinylidene chloride polymer lilms suffered the disadvantage of becoming brittle and losing strength and other qualities at low temperatures. Prior art attempts to plasticize these copolymers have not generally been successful in overcoming those problems. The compatibility of liquid plasticizers with vinylidene chloride polymers is restricted which limits low temperature llexibility. Such liquid plasticizers also have a tendency to bleed out of the composition which is undesirable for packaging of certain foods.

Accordingly, it is a principal object of this invention 3,l5,49l Patented Jan. 12, 1965 8 carbon atoms, acrylic acid, acrylamide, vinyl alkyl ethers, vinyl alkyl ketones, acrolein, allyl esters and ethers, bntadieneand chloropropene. Known ternary compositions also may be employed advantageously. Representative of such polymers are those composed of at least 70% by weight of vinylidene chloride with the remainder made up of, -for example, acrolein and vinyl chloride, acrylic acid and acrylonitrile, alkyl acrylates and alkyl methacrylates, acrylonitrile and butadiene, acrylonitrile and itaconic acid, acrylonitrile and vinyl acetate, vinyl propionate, or vinyl chloride, allyl esters or ethers and vinyl chloride, butadiene and vinyl acetate, vinyl propionate, or vinyl chloride and vinyl ethers and vinyl chloride. Quaternary polymers of similar monomeric composition will also be known.

The rubber-like copolymers which impart low temperature liexibility to the vinylidene chloride polymer are copolymers of (l) an open chain aliphatic conjugated diolelin having from 4 to about 9 carbon atoms, such as butadiene or isoprene, with (2) lower alkyl-lower alkenyl ketones, such as methyl isopropenyl ketone, ethyl vinyl ketone, and methyl vinyl ketone. The conteml plated copolymers are rubber-like elastomers. Such elastomers have a Mooney viscosity at 212 F. of l0 to Y140, preferably in the range of to 70. The rubberlike copolymers are known and may be prepared by copolymerizing the monomers in aqueous emulsion as, for

Y example, by the procedure disclosed in U.S. Patent to provide polymeric compositions based on polymers of vinylidene chloride which compositions retain their ilexibility and other properties at low temperatures, such as are encountered in refrigerated foodstuls and frozen foodstuffs.

Itis a further object of the invention to provide polymeric compositions which have an advantageously low melt viscosity which facilitates the fabrication of lilms by extrusion and the like.

It is a further object of the invention to provide polymeric compositions which do not discolor on exposure t0 light.

It is a further object of this invention to provide polymeric compositions which are relatively impermeable to water vapor and other gases.

The polymeric composition of this invention comprises a blend of (I) from 70 to 95% by weight of the composition of a crystalline polymer consisting of (a) about 70 to 100% by weight of vinylidene chloride and (b) 0 to 30% by weight of at least one monoethylenically unsaturated comonomer and (II) from 5 to 30% by weight of the composition of a rubber-like copolymer consisting of (l) from 70 to 95 by weight of a conjugated dioletin and (2) 5 to 30% by weight of a lower alkyl-lower alkenyl-ketone.

The crystalline vinylidene chloride polymers usable in this invention are Well known and may be prepared by interpolymc-:rizing vinylidene chloride with known comonomers. Typical of the normally crystalline polymeric materials falling within theV advantageous delinition are the polymers and copolymers of at least 70% by weight of vinylidene chloride with the remainder composed of one or more other monoethylenically unsaturated comonomers exemplary of which are vinyl chloride, vinyl acetate, vinyl propionate, acrylonitrile, alkyl and aralkyl acrylates having alkyl and aralkyl groups of up to about Y 70% butadiene and 30% methyl isopropenyl ketone to,V

, The polymeric blends ofthe invention may include plasticizers, such as dioctyl phthalate, dibutyl sebacate, and the like, in the range of about 2 to 10% by weight of the composition. The polymers blend may also in# clude antioxidants, light stabilizers, and other additivesl known in the art which do not deleteriously atleet the properties of the lm.

The polymer blends of the invention are preferably prepared by mixing latexes of the vinylidene chloride polymers and of the rubber-like copolymer in the proper proportions, coagulating the latex blend with alum orV other known coagulants and recovery of dried polymer as is known in the art. The polymer blends are preferably extruded in tube form, stretched and oriented by the bubble technique and slit to form lilms as is known in this art. The compositions are useful in other processes, such as molding, slot extrusion, and other thermal fabrication techniques, to form lms, libers, foils, molded articles, and other forms having the superior properties.

The products of this invention will be illustrated with the following examples in which all percentages and parts :are by weight. l

EXAMPLE 1 A latex containing 34% solids of crystalline copolymer composed of 73% by weight Vinylidene chloride and 27% by weight of vinyl chloride was prepared by emulsion polymerization, utilizing potassium persulfate as the catalyst and the dihexyl ester of the sodium salt of sulfosuccinic acid as the emulsilier in a manner well known in the art.

Several batches of rubbery latexes were prepared from form latexes having 46% solids content utilizing potassium persulfate as the catalyst and the dihexyl ester of oxidant.

The vinylidene chloride latex and the rubbery copolymer latexes Were blended in desired proportions, coagulatcd, and dried and the polymer blend recovered.

Unplasticized flow moldings were made from certain of the polymer blends. In one case of dibutyl scoiacate was added as a plasticizer. Samples of the unblended 4 Tables III and IV present data on physical properties of 73% vinylidene chloride-27% vinyl chloride modiied with butadiene-methyl isopropenyl ketone copolymer, both with and without 5% dibutyl sebacate as a 5 plasticizer. The column headed percent MIK is the percentage of methyl isopropenyl ketone in the ruibbery vinylidene chloride polymer were used as one comparison copolymer.

and unblended vinylidene chloride polymer plus 5% di- Table III butyl sebacate as a further comparison. llow moldings MOLDINGS were also made of these samples in identical manner to 19 [10% rubber copolymerin blend] the previously mentioned moldings.

Other samples of the polymer blends were thermally Percent Melt Viscosity Flexuml extruded using standard bubble techniques into oriented Sample NoA MIK (Poisesxio) Modu1us, C. films having a thickness of 0.001 inch. In each case, dibutyl sebacate was employed as the plasticizer. 12

The following tables summarize the results of the physigg 82 :2: 5 cal properties determined on the moldings and the orien- 30 170 -5 0 ted films.

In Tables I and II, the physical properties of 73% Table IV vinylidene chloride 27% vinyl chloride copolymer plus 2O various percentages of 70% butadiene-30% methyl iso- ORENTED FILMS pI-openylA ketone polymers are tabulated both with Gr [10% rubber copolymer -i- 5% dibutyl sebacate plasticizer] without the addition of 5% dibutyl sebacate as a plasti- I .L e Sample Percent PercentT AT O Cold cizer. The ccolumn headed Rubber Content indicates u NO MIK Visible Yellow Trail WVTR Flex the amount oi the rubbery copolymer in the film. 2a Range Table I 15 85.5 3.2 4.8 0.6 8 MOLDINGS s3. 6 5. 7 7. 6 1.0 5 87.1 4.7 10.8 1.1 4 87.3 5.5 18.4 1.7 3 Flexural Second 30 Sample No. Rubber Content Moiulus, Point 'lgran- 0- SIUOH: C- Tables V and VI present the physical properties of 73% Vinylidene chloride 27% Vinyl chloride modied For com arison: u A l L Ij None (Control) +11. 0 1.0 with 15% of various rubbery copolymers, both Withand 2 commi-F517J Pinstr- -120 26.0 35 Without the addition of 5% dibutyl sebacate plasticizer.

eizer.

Table V 5.0 12.0 (7 9. 0 15. 0 MOLDINGS 20 13.5 12.0

1072+512, Plasticizer... 30. 0 85. 0 [15% rubber copolymer] In all of the tables of this example, the column headings Sample No, BI'Y ltl@ have the following meanlngs: n Melt viscosity (poises): Expresses the llowability of a gig :-g

plastic at 180 C. and 237 lbs/in.2 pressure between 25 220 13:5

parallel platens at essentially zero shear rate. 30 190 l1-0 Flexural modulus C.): The temperature at which the unplasticized molded strip possesses a modulus of Table VI 2.5 10-5 lbs/1n.2 in exure. ORIEYTED FILMS Percent transmission (T): Percent of visible range 4,000- y L t L y 8,000 A. transmitted through one mil oriented lm. [15% rubber copolymer 5% dlbutyl Schaam plastlcizer] AT: Degree of yellowness. Obtained from the difference s 1 P t P tT AT O C 1d mp @T0911 61'0611 O 0f tfansfmslons at 6200 A and 4200 A No. MIK Visibie Yeiiow Trails. WVTR Fiex OZ transmission: CC. at STP/ in.2/24 hrs/m11 at l Range atm. driving force. M WVTR: Water vapor transmission rate. Gins./ 100 in.2/ 24 "o l gg 1115.? g-ihr/mll. at 100 and relative 25 88:1 3:9 21:1 1:4 8+ *Cold ex: Number of hand exes at 18 C. (0 F.) to 24 30 88.9 4.8 40.0 2.8 5

produce rupture.

Table Il ORIENTED FILMS Tensile Elongation Tear Strength Drop Strength (percent) grains) Percent Shrink Impact Sample N o. Rubber Content (psi.) 18 C., KgilmJ L C L C L C 100 C. 85 C.

For comparison:

Contrari-5% P1a5ticizer 6,000 14,000 110 85 185 40 56 2s 5.5 This invention:

s 10%+5% Plasticizer 6,500 11,500 160 85 138 (l) 45 28 12.8

1 Would not tear.

rml?

Tables VII and VIII present data on physical properties i i Table XI p of 73% vinylidcne chloride-27% vinyl chloride copolyrner modified with various percentages of a rubber co- Composition of Vinylidene Percent Flex. Mod. Melt polymer of 80% butadiene 20% methyl isopropenyl Chloride com? 70/30 X105 at 0C Cold Viscosity LetOne. 5 mer (Percent Rubber (p.s.i.)1 Point,2 Poise Vinylidene Comp. C. Table VII Chloflde) [v MOLDINGS 5.7 22 165,000 myhdene chloride copolymer -lcopolymer of 80% butadiene-20% MIK] 10 1. 7 19 135,000 20 0.8 15 185,000 30 0.6 13 250,000 lcrcent Melt Viscosity Flexural 0 4.1 2l 110, 000 Sample No. Copolymer (PoisesXlOS) Modulus, C. 10 1 6 15 85,000 20 0.7 19 145,000 30 0.3 11 320,000 0 180 8. 0 o 3. 2 17 125,000 195 7. 0 10 1. 4 12 115, 000 v 210 -0. 5 20 0. 6 3 164, 000 340 8. 0 3o 0. 3 -11 400, 000 310 13.5

1 Flexural Modulus at 0 C., the actual modulus p.s.i. at 0 C. 2 Cold Point is the "l`rst large change in the slope of the tlexu'lnodulus Table VIII 20 vs. temperature curve as the temperature decreases from +5 v ORIENTED FILMS From the data presented, it can be seen that the ad- [Blends OfTable VH1-5% ibutylsebacf plestieizer] dition of the indicated amounts of the specified elastomerio polymers to the normally crystalline vinylidcne Sample Percent Percent'l AT O2 Cold a feciabl No. copoly- Visibie Yellow Trans. WVTR mex Chlorlde copolymers results lll blends h avlll pp y mor Rango enhanced phys1cal propert1es over the vinylidcne chloride copolymers whether plasticized or unplasticized and 0 89.5 2.9 3.a 0.5 1 whether stabilized or unstabilized. With regard to the '5 83-8 7-l 4-4 0-8 2 latter, a composition was prepared by intimately blend- 10. 83.6 5.1 7.6 1.0 5 15 82.6 6.9 11.7 1.1 20+ 111g 10% by weight of a copolymer of 70% butadiene 20 83-8 5-3 17-0 1-4 20+ 30 and 30% methyl isopropenyl ketone with 90% of a Tables IX and X present the data on physical properties of 73% vinylidcne chloride-27% vinyl chloride modiied with various proportions of a rubbery copolymer of 70% butadiene-30% isopropenyl ketone, with or without 5% dibutyl sebacate as a plasticizer.

Table IX MOLDINGS [Vinylidene chloride copolymer rlzgpolymer of 70% butadiene-30% Sample No. Percent Melt Viscosity Flexnral Copolymer (PoisesX103) Modulus, C.

'I' able X ORlENTED FILMS [Blends of Table 1X -l- 5% dibutyl sebacate plasticizer] Sample Percent Percent T AT O2 Cold No. Copoly- Visible Yellow Trans. WVTR Flex mer Range EXAMPLE 2 Latexes composed of 85% vinylidene chloride-15% Vinyl chloride, 80% vinylidcne chloride-20% vinyl chloride, and 73% vinylidene chloride-27% Vinyl chloride were prepared as in Example 1. A rubbery copolymer of 70% butadiene-30% methyl isopropenyl ketone was prepared as in Example 1 and unplasticzed moldings were formed as in Example 1 containing various proportions of the rubbery copolymer. The following table presents the data:

copolymer of 73% vinylidcne chloride and 27% Vinyl chloride. T'his blend was fabricated by thermal extrusion without further plasticization or stabilization into an oriented film. The properties of this lm showed about the same magnitude improvement over an unblended vinylidcne chloride copolymer film as is evidenced in the foregoing examples.

From all of the above data it can be seen that incorporation of the butadiene methyl isopropenyl copolymers into normally crystalline vinylidene chloride polymers produces most favorable lms and other articles for low temperature utility while retaining the desirable physical characteristics of those vinylidcne chloride polymers.

We claim:

1. A polymeric composition comprising a blend of (l) from 70 to 95% by weight of the composition of a normally crystalline polymer selected from the group consisting of polyvinylidene chloride and interpolymers of at least about 70% by weight of vinylidcne chloride with up to about 30% by weight of at least one other monoethylenically unsaturated comonomer and (II) complementarily from 5 to 30% by Weight of the composition of a rubber-like copolymer consisting of (1) from 70 to 95 by weight of open chain aliphatic conjugated diolen having from 4 to about 9 carbon atoms and (2) 5 to 30% Vby weight of a lower alkyl-lower alkenylketone.

2. The composition as claimed in claim l wherein said normally crystalline. polymer Vis a copolymer of vinylidene chloride and vinyl chloride.

3. The composition as claimed in claim 2 wherein said normally crystalline polymer is a copolymer of 73% by weight of vinylidcne chloride and 27%v by weight of vinyl chloride.

4. The composition as claimed in claim 1 wherein said rubber-like copolymer is a copolymer of butadiene and methyl isopropenyl ketone.

5. The composition as claimed in claim 1 containing from 2 to 10% by weight of the composition of a plasticizer for a crystalline vinylidcne chloride polymer.

6. The composition as claimed in claim 5 wherein said plasticizer is dibutyl sebacate.

7. The composition as claimed in claim l wherein said composition contains an antioxidant.

8. The composition as claimed in claim 7 wherein said antioxidant is 2,4dimethyl-6(l-methylcycloheXyD- phenol.

9. A polymeric composition comprising a blend of (I) from 70 to 95% by Weight of the composition of a normally crystalline .polymer selected from the group consisting of polyvinylidene chloride and copolymers of at least about 70% by weight of polyvinylidene chloride with up to about 30% by weight of vinyl chloride and (II) from to 30% by weight of the composition of a rubber-like copolymer consisting of (1) from 70 to 95 by weight of butadiene and (2) 5 to 30% by weight of methyl isopropenyl ketone.

10. The composition as claimed in claim 9 containing from 2 to 10% by weight of the composition of dibutyl sebacate.

11. An oriented lm having improved exibility at temperatures below 32 F. composed of a homogeneous blend of (I) from 70 to 95% by weight of the film of a normally crystalline polymer selected from the group consisting of polyvinylidene chloride and interpolymers of at least about 70% by weight of vinylidene chloride with up to about 30% by weight of at least one other monoethylenically unsaturated comonomer and (II) from 5 to 30% by weight of the iilm of a rubber-like copolymer consisting of (l) from 70 to 95% byweight of a co-njugated diolefin and (2) 5 to 30% by weight of a lower alkyl-lower alkenyl-ketone.

12. The oriented lm claimed in claim l1 wherein said monoethylenically unsaturated comonomer is vinyl chloride. 13. A molded article composed of a homogeneous blend of (I) from 70 to 95% by Weight of the article of a normally crystalline polymer selected from the group consisting of polyvinylidene chloride and interpolymers of at least about 70% by weight of vinylidene chloride with up to about by weight of at least one other monoethylenically unsaturated comonomer and (1I) from 5 to 30% by weight'of the article of a rubberlike copolymer consisting of (l) from to 95% by weight of a conjugated dioleiin and (2) 5 to 30% by weight of a lower alkyl-lower a1kenylketonel 14. A molded article claimed in claim 13 wherein said monoethylenically unsaturated comonomer is vinyl chloride.

References Cited in the tile of this patent UNITED STATES PATENTS 2,469,721 Gidley May 10, 1949 3,005,796 Dreisbach Oct. 24, 1961 3,033,812 Isaccs et al. May 8, 1962 OTHER REFERENCES Buttrey: Plasticizers, Franklin Publishing Co., New Jersey, chapter 4, p. 76, 1960.

Miall: A New Dictionary of Chemistry, Intersciencc Publishers Inc., New York, p. 48, 1961. 

1. A POLYMERIC COMPOSITION COMPRISING A BLEND OF (I) FROM 70 TO 95% BY WEIGHT OF THE COMPOSITION OF A NORMALLY CRSTALLINE POLYMER SELECTED FROM THE GROUP CONSISTING OF POLYVINYLIDENE CHLORIDE AND INTERPOLYMERS OF AT LEAST ABOUT 70% BY WEIGHT OF VINYLIDENE CHLORIDE WITH UP TO ABOUT 30% BY WEIGHT OF AT LEAST ONE OTHER MONOETHYLENICALLY UNSATURATED COMMONOMER AND II) COMPLEMENTARILY FROM 5 TO 30% BY WEIGHT OF THE COMPOSITION OF A RUBBER-LIKE COPOLYMER CONSISTING OF (1) FROM 70 TO 95% BY WEIGHT OF OPEN CHAIN ALIPHATIC CONJUGATED DIOLEFIN HAVING FROM 4 TO ABOUT 9 CARBON ATOMS AND (2) 5 TO 30% BY WEIGHT OF A LOWER ALKYL-LOWER ALKENYLKETONE. 